Hydrotreating is an essential step in the refining of crude petroleum, the major purposes of which is for (i) the conversion of organosulfur and organonitrogen compounds to hydrogen sulfide and ammonia, respectively, (ii) the removal of metals and (iii) the hydrogenation of olefins and aromatics present in the petroleum fraction. Catalysts for the hydrotreating process are metal oxides which have been sulfided prior to use (presulfided). By presulfiding under carefully controlled conditions, coke formation, which leads to catalyst deactivation by plugging the catalyst pores, is minimized.
In copending patent application Ser. No. 675,165 filed Nov. 27, 1984, a presulfiding agent, process of presulfiding an oxide hydrotreating catalyst and the process of hydrotreating petroleum is disclosed. The presulfiding agent is a dialkyl polysulfide of the formula: R(S).sub.x R.sup.1 wherein R and R.sup.1 are C.sub.1 -C.sub.20 alkyl groups and x an average number is in the range of 2 to 8. The process of presulfiding the oxidie hydrotreating catalyst requires that no reducing agent be introduced into the presulfiding procedure.